Investigators in this section are continuing to refine existing methodologies for the study of cortical functioning on the basis of positron emission tomography (PET) and electrical brain mapping procedures in humans. As wide variability has been noted in normals and patient groups in terms of PET determinations of cerebral glucography, efforts have been made to control for this. First, we have attempted to control behavioral variability through having subjects participate in specific psychological tasks during these studies. This has included the use of a somatosensory stimulus paradigm and most recently an auditory continuous performance task (cpt). Secondly, we have attempted to use methods of statistical analysis that deemphasize absolute glucose metabolic rate in favor of comparative regional rates. Using these approaches, schizophrenic and affectively disordered patients appear to differ from normals. For example, psychiatric patients appear to have somewhat lower ratios of frontal to posterior cortical rates of glucose metabolism although the interpretation of these findings remain obscure. The ratios do not represent an absolute lowering of glucose metabolic rates in the frontal cortex of psychiatric patients. Schizophrenic patients who improve on neuroleptics show a further diminution in the normal anteroposterior gradient. Other preliminary findings suggest that schizophrenic patients have elevated glucose metabolism in both temporal lobes which appears to increase in the medicated state. By electrophysiology, a diminution of the N120 component of the somatosensory evoked potential has been observed in normals in response to a series of similar somatosensory stimuli. This habituation which is most prominent in somatosensory stimuli. This habituation which is most prominent in somatosensory does not appear to occur in schizophrenic patients, but appears normally in patients with affective disorders. This finding would appear related to our recent findings in the PET where the primary somatosensory area changes observed in normals appear to be diminished in schizophrenics.